Method and apparatus for liquid disinfection using light transparent conduit

ABSTRACT

Some demonstrative embodiments of the invention include an illumination-based liquid disinfection device. The disinfection device may include, for example, a light transparent conduit to carry a flowing liquid to be disinfected, the conduit having an inlet to receive the liquid and an outlet to discharge the liquid, a substantially light transparent sleeve having external dimensions smaller than the internal dimensions of the conduit, the sleeve positioned within the conduit substantially perpendicular to the axis of symmetry of the conduit and a light source positioned within the sleeve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 13/892,328 filed on May 13, 2013, issued as U.S. Pat. No. 9,320,818on Apr. 26, 2016. U.S. application Ser. No. 13/892,328 is a Continuationapplication of U.S. application Ser. No. 11/917,878 filed on Jun. 8,2010 which is a National Phase of PCT Application No. PCT/IL2007/001409,International filing date Nov. 14, 2007, claiming the benefit of U.S.provisional patent application 60/858,727, filed on Nov. 14, 2006.

BACKGROUND OF THE INVENTION

Ultraviolet liquid disinfection systems using UV light source locatedwithin a metallic chamber through which the liquid flow have been longknown. The walls of such a metallic chamber absorb most of the incidentUV light and light rays emitted from the UV light source traversethrough the water once and are essentially absorbed by the metal.Accordingly, such systems do not utilize the light source in anefficient manner There is a need for a UV disinfection system that wouldbe more efficient than existing systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanied drawings in which:

FIGS. 1A and 1B are conceptual illustrations of a disinfection systemaccording to some demonstrative embodiments of the invention;

FIG. 2A is an illustration of an exemplary disinfection system accordingto some demonstrative embodiments of the invention;

FIG. 2B is a cross sectional view of the exemplary disinfection systemof FIG. 2A;

FIG. 3 depicts an exemplary illustration of a UV-transparent conduitaccording to some demonstrative embodiments of the invention;

FIG. 4 is a side view of a conceptual illustration of an exemplaryUV-transparent conduit having a reflective coating on portions of itssurface according to some demonstrative embodiments of the invention;

FIGS. 5A-5C are schematic illustrations of conduits according to somedemonstrative embodiments of the invention;

FIGS. 6A and 6B are illustrations of disinfectors having flow-formingobjects according to some demonstrative embodiments of the invention;

FIG. 7 is a cross section schematic illustration of a non-cylindricalsleeve according to some demonstrative embodiments of the invention;

FIG. 8 is a conceptual illustration of an exemplary disinfection systemhaving a patterned sleeve according to some demonstrative embodiments ofthe invention;

FIG. 9 is a conceptual illustration of an exemplary disinfection systemhaving a non-cylindrical light source according to some demonstrativeembodiments of the invention;

FIG. 10 is a schematic illustration of a 2-pipe disinfection systemaccording to some demonstrative embodiments of the invention.

FIGS. 11A-11C are exemplary illustrations demonstrating the modularnature of a disinfection system according to embodiments of theinvention;

FIGS. 12A-12C are schematic illustrations of light flux distributionwithin an exemplary conduit based on computer simulations according toembodiments of the invention;

FIG. 12D is a dose distribution histogram associated with the simulationof FIGS. 12A-12C;

FIGS. 13A-13B are schematic illustrations of light flux distributionwithin a stainless steel conduit based on computer simulations accordingto embodiments of the invention; and

FIG. 13C is a dose distribution histogram associated with the simulationof FIGS. 13A-13B.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the drawings have not necessarily been drawnaccurately or to scale. For example, the dimensions of some of theelements may be exaggerated relative to other elements for clarity orseveral physical components included in one functional block or element.Further, where considered appropriate, reference numerals may berepeated among the drawings to indicate corresponding or analogouselements. Moreover, some of the blocks depicted in the drawings may becombined into a single function.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those of ordinary skill in the artthat the present invention may be practiced without these specificdetails. In other instances, well-known methods, procedures, componentsand circuits may not have been described in detail so as not to obscurethe present invention.

Some demonstrative embodiments of the invention include an ultraviolet(UV) disinfection system having a conduit to carry liquid to bedisinfected and an illumination source located inside a transparentsleeve positioned substantially perpendicular to the longitudinal axisof symmetry of the conduit and the direction of flow of the liquid.

It will be appreciated that the liquid disinfection process may includeinactivation or removal of any organism, bacteria, microorganism, being,creature, microbe, germ, virus, organic contaminator, non-organiccontaminator, oxidizeable toxic or contaminator; any cumulative noxiousspecies of biological or chemical origin; any oxidizing particle,fragment or element, e.g., Hydrogen peroxide or Titanium dioxide,intended to oxidize a contaminator and/or the like. Some demonstrativeembodiments of the invention may refer to using ultraviolet (UV) lightto disinfect the liquid and/or to oxidize particles within the liquid.However, it will be appreciated by those skilled in the art, that inother embodiments of the invention, light of any other suitable spectrummay be used.

Reference is now made to FIGS. 1A and 1B, which conceptually illustratea disinfection system according to some demonstrative embodiments of theinvention. A disinfection system 100 may include a tube or conduit 101to carry liquid to be disinfected, one or more substantiallylight-transparent sleeves 102 positioned within conduit 101substantially perpendicular to its longitudinal axis of symmetry 109 andone or more light sources 104, each positioned within a respectivesleeve 102. According to embodiments of the invention light sources 104may be UV light sources capable of emitting light at 254 nm Conduit 101may have an inlet 106 to receive from an external liquid pipe the liquidto be disinfected and an outlet 108 to discharge the liquid via anexternal discharge pipe. System 100 may further include adaptors 110 toconnect conduit 101 to the external liquid pipes. The adaptors maycomprise O-rings to ensure water-tight connections between the externalpipes and the conduit.

Conduit 101 may be substantially made of UV-transparent glass, such asquartz. UV-transparent sleeves 102 may be for example quartz or Teflon®sleeves. Each Sleeve 102 may have external dimensions smaller than theinternal dimensions of conduit 101 such that liquid may flow withinconduit 101 around sleeves 102. Both ends of sleeve 102 may extend fromthe walls of conduit 101 to enable replacement of light source 104within sleeve 102. Light sources 104 may illuminate the liquid to bedisinfected when flowing in the conduit. In this configuration, theliquid within conduit 101 may act as a waveguide and at least part ofthe light, for example, at least half of the emitted UV intensity, maybe totally-internally reflected at the interface of the UV-transparentconduit 101 and the air surrounding it. Conduit 101 may be locatedinside a protective metal sleeve with an air gap between the conduit andthe sleeve, as shown for example, in FIG. 2B. The total internalreflection (TIR) effect is demonstrated in FIG. 1B.

Although the invention is not limited in this respect, light source 104may generate UV light of a suitable UV-germicidal spectrum. For example,light source 104 may include one or more UV lamps, e.g., a low-pressureUV lamp, a low-pressure high output UV lamp, a medium-pressure UV lamp,a high-pressure UV lamp, and/or a microwave-excited UV lamp, as are allknown in the art.

According to embodiments of the invention, the liquid may act as awaveguide and at least part of the light, for example, at least half ofthe emitted UV intensity, may be totally-internally reflected at theinterface of the glass conduit and air surrounding it. According toother embodiments of the invention, at least 70% of the emitted UVintensity may be totally-internally reflected at the interface of theglass conduit and air surrounding it. As shown, in FIG. 1B, the liquidto be disinfected may flow around each of light sources 104. In such aconfiguration, the system may include an additional light source toenable disinfection of the liquid to the required level even when one ofthe light sources 104 is fully or partially dysfunctional. For example,the disinfection process may continue while a non-functional lightsource is being replaced or fixed.

It should be noted that embodiments of the present invention, in whichlight sources 104 are located substantially perpendicular to thedirection of flow of the liquid within conduit 101 may ensure that eachlight source is capable of illuminating substantially the entire flow ofliquid when the flow traverses that particular light source.

Reference is now made to FIG. 2A, which shows an exemplary disinfectionsystem and to FIG. 2B, which is a cross sectional view of the exemplarydisinfection system according to some embodiments of the invention. Anexemplary disinfection system 200 may include a substantiallyUV-transparent conduit 201 to carry liquid to be disinfected,substantially UV-transparent sleeves 202A and 202B positioned withinconduit 201 substantially perpendicular to its axis of symmetry 209 andone or more UV-light sources 204, each positioned within a respectivesleeve 202. In this exemplary configuration, sleeves 202A and 202B areorthogonal to each other.

It should, however, be understood to a person skilled in the art, thataccording to embodiments of the present invention, UV-transparentsleeves 202 may be positioned with respect to each other, at anyrotational angle around the longitudinal axis of symmetry 209 of conduit201. According to other embodiments of the present invention,UV-transparent sleeves 202 may be positioned at any rotational anglearound other axis of symmetry of conduit 201. Although a symmetricalcylinder-shaped conduit is shown, it should be understood to a manskilled in the art that the conduit may have other shapes, notnecessarily symmetrical, as described in detail with respect to FIG.5A-5C.

Conduit 201 may be located inside a protective metal tube 203 forming anair gap 208 between conduit 201 and metal tube 203. Although the scopeof the present invention is not limited in this respect, external tube103 may include a see-through window 210 made of transparent materialsuch as glass, plastic or any other suitable material to enable anoperator to view conduit 201 and a cover 212 to cover window 210 whendesired. Although in the exemplary illustration of FIG. 2A, a singlesee-through window is shown, it should be understood to a person skilledin the art that the invention is not limited in this respect andaccording to embodiments of the present invention tube 203 may includemore than one see-through window at any size and/or shape.

Reference is now made to FIG. 3, which depicts an exemplary illustrationof a conduit having four sleeves according to some demonstrativeembodiments of the invention. The exemplary conduit 301 of FIG. 3includes four UV-transparent sleeves 302A-302D positioned within conduit301 substantially perpendicular to its longitudinal axis of symmetry309. In this exemplary configuration, pairs of adjacent sleeves areorthogonal to each other. Accordingly, sleeves 302A and 302B areorthogonal to each other; sleeves 302B and 302C are orthogonal to eachother; and sleeves 302C and 302D. Further, pairs of alternating sleevesare parallel to each other. Accordingly, sleeves 302A and 302C areparallel to each other; and likewise sleeves 302B and 302D are parallelto each other. It should, however, be understood to a person skilled inthe art, that according to embodiments of the present invention,UV-transparent sleeves 302 may be positioned with respect to each other,at any rotational angle around the axis of symmetry 309 of conduit 301.Sleeves may be fused to conduit 301 to form a single glass structure.

According to other embodiments of the present invention, sleeve 202 maybe attached to conduit 301 using housing, adaptors, connectors or anysuitable means known in the art. For example, each of areas 316A-316Dmay be a metal housing for one of sleeves 302A-302D. The metal housingmay be coated on its interior surface with a reflective coating toincrease the efficiency of the disinfection process. According toembodiments of the invention, the reflective coating may be coated witha UV-transparent, UV resistive and bio-compatible coating, for example aTeflon® coating.

Although, the sleeves are illustrated as being cylindrical, it should,be understood to a person skilled in the art that embodiments of theinvention are not limited in this respect and the sleeve may have othersuitable shapes, such as hydrodynamic shapes, as detailed below withrespect to FIG. 7.

Reference is now made to FIG. 4, which conceptually illustrates a sideview of an exemplary conduit having a reflective coating on portions ofits surface according to some embodiments of the invention. A sleeve 402may be positioned within conduit 401 such that sleeve 402 issubstantially perpendicular to the longitudinal axis of symmetry 409 ofconduit 401. UV-light source 404 may be positioned within sleeve 402. Asboth sleeve 402 and conduit 401 are substantially transparent to UVlight, the liquid may act as a waveguide and at least part of the light,for example, rays 410 and 411 may be totally-internally reflected at theinterface of conduit 401 and the air surrounding it 408.

Still, rays such as ray 413 having an angle with the surface of theconduit above a critical angle cannot undergo total internal reflection(TIR). Such a ray is transmitted outside the liquid after traversing theliquid only once. Conduit 401 may include one or more mirrors or UVreflective coating areas 407 to reflect non-guided rays, for example,ray 412 back into the liquid.

According to some embodiments of the present invention, at leastportions of the exterior surface of conduit 401 may be coated with UVreflective coating 407 to produce rear surface mirror effect, e.g., toallow a larger portion of the light from light source 404 to illuminatethe liquid flowing in conduit 401. Coating 407 may reflect back into theliquid additional light rays reaching the surface in relative proximityto sleeve 402. Reflective coating 407 may comprise aluminum deposition,gold deposition or multi-layer dielectric material. Any other suitablereflective coating may be used. According to other embodiments of theinvention, the entire surface of the conduit may be coated withreflective coating to enhance the back-mirror effect.

Although the scope of the present invention is not limited in thisrespect, at least a portion of conduit 401, e.g., area 414 surroundinglight source 404 may be from a material having UV-reflection properties,for example, aluminum or any other metal. Reflecting area 414 mayreflect back into the liquid non-guided light rays that cannot undergoTIR, such as ray 413. Reflecting area 414 may include a UV-reflectingcoating on its inner surface or may be covered by a thin sheet made ofmaterial having UV-reflecting properties. The UV-reflecting coating orsheet may be protected against water damage by coating it with aUV-resistive, UV-transparent coating such as Teflon®.

Reference is now made to FIGS. 5A, 5B and 5C, which depict schematicillustrations of conduits having varying diameters along their lengthsaccording to some demonstrative embodiments of the invention. The shapeof the conduit may be pre-determined to increase the efficiency of thedisinfection process. According to embodiments of the present invention,the internal diameter of conduit 501 may vary along its length, asdepicted in the demonstrative illustration of FIGS. 5A, 5B and 5C. Thespecific shape of the conduit may affect the liquid flow pattern and theshape may be pre-determined in order to increase the overall efficiencyof the disinfection system. It should be understood that conduit 501 mayhave any other symmetrical or non-symmetrical shape.

Reference is now made to FIGS. 6A and 6B, which depict schematicillustrations of a portion of disinfection systems having flow-formingobjects according to some embodiments of the present invention. Each ofdisinfection systems 600A and 600B may include a conduit 601 to carryliquid to be disinfected, a substantially UV-transparent sleeves 602positioned within conduit 601 substantially perpendicular to itslongitudinal axis of symmetry and a UV-light sources 604 positionedwithin sleeve 602. Conduit 601 may include one or more objects 614affixed to the conduit. As illustrated in FIG. 6A, objects 614 may beattached to a protrusion to be located in relative distance from thesurface of the conduit. As illustrated in FIG. 6B, objects 614 may beattached to the surface of the conduit or located in relative proximityto the surface. Objects 614 may be pre-designed and may be located inspecific positions in conduit 601 to affect the liquid flow pattern.Additionally or alternatively, UV-transparent objects and/orUV-scattering objects and/or UV-reflective objects may be affixed,attached or added to conduit 601. The flow-forming objects may affectthe liquid flux and the distribution of liquid tracks and the objectsshape and location may be pre-determined in order to increase theoverall efficiency of the disinfection process. The light scatteringobjects and/or light reflective objects may influence the spatialdistribution of UV light intensity and the objects shape and locationmay be pre-determined in order to increase the overall efficiency of thedisinfection process.

Reference is now made to FIG. 7, which depict schematic cross sectionillustration of non-cylindrical sleeve according to some demonstrativeembodiments of the invention. According to embodiments of the presentinvention, sleeve 702 may have a hydrodynamic shape to prevent theformation of liquid stagnation zone where liquid may flow at a lowvelocity in proximity to sleeve 702 at the area facing the outlet of theconduit. The specific shape of sleeve 702 may be designed to improvelight distribution and liquid flow pattern in order to increase theoverall efficiency of the disinfection system. It should be understoodto a person skilled in the art that sleeve 702 having a non-cylindricalshape may be positioned within a substantially UV-transparent conduitsubstantially perpendicular to the direction of liquid flow.Alternatively, the non-cylindrical sleeve may be positioned withinnon-transparent containers such as stainless steel conduits or reactors.

Reference is now made to FIG. 8, which is a conceptual illustration ofan exemplary disinfection system having a patterned sleeve according tosome demonstrative embodiments of the invention. A sleeve 802 may bepositioned within conduit 801 such that sleeve 802 is substantiallyperpendicular to the longitudinal axis of symmetry of conduit 801.UV-light source 804 may be positioned within sleeve 802. As both sleeve802 and conduit 801 are substantially transparent to UV light, theliquid may act as a waveguide and at least part of the light may betotally-internally reflected at the interface of conduit 801 and itssurroundings. For another portion of the light that cannot undergo TIR,conduit 801 may include one or more mirrors or UV reflective coatingareas 807 to reflect rays back into the liquid. Still, certain rays mayevade both TIR and the UV reflective areas.

According to embodiments of the invention, sleeve 802 may include one ormore objects 805 located in specific positions and shaped in order toinfluence the light distribution inside conduit 801. Object 805 may beUV-scattering or UV-reflecting objects made of any suitable material.For example, ray 820 is directed toward area 821, which is not coatedwith reflective coating. Accordingly, in a non-patterned sleeve such aray would traverse the liquid for a short distance before exiting theconduit via area 821. Instead by using sleeve 802, ray 820 may hitobject 805, change its direction (arrow 822) and reach reflective area807 to be reflected back into the liquid.

Although, the patterned sleeve is described as being positioned within asubstantially UV-transparent conduit substantially perpendicular to thedirection of liquid flow, it should, be understood to a person skilledin the art that embodiments of the invention are not limited in thisrespect and embodiments of the invention are likewise applicable tousing such a patterned sleeve at any position relative to the liquidflow within any container or conduit including non-transparentcontainers such as stainless steel conduits or reactors.

Reference is now made to FIG. 9, which is a conceptual illustration ofan exemplary disinfection system having a non-cylindrical light sourceaccording to some demonstrative embodiments of the invention. A sleeve902 may be positioned within conduit 901 such that sleeve 902 issubstantially perpendicular to the longitudinal axis of symmetry ofconduit 901. UV-light source 904 may be positioned within sleeve 902. Asboth sleeve 902 and conduit 901 are substantially transparent to UVlight, the liquid may act as a waveguide and at least part of the lightmay be totally-internally reflected at the interface of conduit 901 andits surroundings. For another portion of the light that cannot undergoTIR, conduit 901 may include one or more mirrors or UV reflectivecoating areas 907 to reflect rays back into the liquid. Light source 904may have a non-cylindrical geometry; for example, its cross section maybe an ellipse or any other desired shape to generated controlled lightdistribution. For example, the shape of the lamp may be directed togenerate a non-circular light distribution such that more light rayswould be directed to the direction of the liquid flow than to thesurface of conduit 901. The specific shape of light source 904 may bedesigned according to the specific characteristics of the system'sgeometry and the disinfection process in order to increase the overallefficiency of the disinfection system.

Although, the non-cylindrical light source is described as beingpositioned within a substantially UV-transparent conduit substantiallyperpendicular to the direction of liquid flow, it should, be understoodto a person skilled in the art that embodiments of the invention are notlimited in this respect and embodiments of the invention are likewiseapplicable to using such a light source at any position relative to theliquid flow within any container or conduit including non-transparentcontainers such as stainless steel conduits or reactors.

Reference is now made to FIG. 10, which depicts an exemplaryillustration of a 2-pipe disinfection system according to embodiments ofthe invention. A disinfection system 140 may include a conduit 141 tocarry liquid to be disinfected. Conduit 141 may include more than onebranch, for example two branches, 143A and 143B to increase the liquidflow. Having more than one branch may enable better control of theinternal pressure in conduit 141. Conduit 141 may have an inlet 146 toreceive from an external liquid pipe the liquid to be disinfected and anoutlet 148 to discharge the liquid via an external discharge pipe.

System 140 may include one or more substantially UV-transparent sleeves142A positioned within branch 143A substantially perpendicular to itslongitudinal axis of symmetry 149A and one or more UV-light sources144A, each positioned within a respective sleeve 142A. System 140 mayfurther include one or more substantially UV-transparent sleeves 142Bpositioned within branch 143B substantially perpendicular to itslongitudinal axis of symmetry 149B and one or more UV-light sources144B, each positioned within a respective sleeve 142B.

It should be understood to a person skilled in the art that although a2-branch conduit is described, embodiments of the invention are notlimited in this respect and a disinfection system according to otherembodiments of the present invention may include more than 2 branchesfor liquid flow.

FIGS. 11A-11C demonstrate the modular nature of an exemplarydisinfection system according to embodiments of the invention. Accordingto some embodiments of the present invention, the liquid flow section ofthe disinfection system may be constructed from two types of modularbuilding blocks, conduit elements 151 and sleeve elements 152. Sleeveelements 152 may include a ring 153 having a UV-transparent sleeve 154positioned within. The internal diameter or ring 153 is larger than theexternal diameter of sleeve 154. Element 152 may further include aUV-light source positioned within sleeve 154. Both ends of element 152may include adaptors, connectors or a screw mechanism to be connected toone or more of conduits 151. Conduit elements 151 may be substantiallymade of UV-transparent material, such as quartz as described in detailabove. The external diameter of conduit 151 may be substantially similarto the external diameter of ring 153. Both ends of conduits 151 mayinclude adaptors, connectors or a screw mechanism to be connected to oneor more of elements 152. The connections between conduits 151 and sleeveparameters 152 may be water-tight connections.

Although the scope of the present invention is not limited in thisrespect, at least one sleeve element 152 and two conduit elements 151may create a conduit set to carry liquid to be disinfected as describedabove. A conduit set may comprise a number of n sleeve elements 152 anda number of n+1 conduit elements 151. For example, as shown in FIG. 11Bconduit 150 may comprise one sleeve element 152 and two conduit elements151. Another example, shown in FIG. 11C, conduit 160 may comprise twosleeve elements 152 and three conduit elements 151.

Although in the exemplary illustration of FIGS. 11A-11C, conduits 150and 160 are shown, it should be understood to a person skilled in theart that the invention is not limited in this respect and according toembodiments of the present invention any combination of n+1 conduitelements 151 and n sleeve elements 152 may be connected to create aconduit set.

Although, embodiments of the present invention are not limited in thisrespect, it is understood and simulated that a pre-designed structureaccording to embodiments of the present invention improves theefficiency of UV disinfection and increase kill probability, namely theprobability to inactivate the entities being in the liquid flowing inconduit 101.

Computer Simulations

Following, are examples relating to illumination flux distributions inaccordance with some demonstrative embodiments of the invention. Itshould be noted that the illumination-flux distributions used in theseexamples are not intended to limit the scope of the invention to anyparticular configuration and/or illumination flux distribution.

FIGS. 12A-12C illustrate computer simulations of light flux distributionwithin an exemplary conduit during a liquid disinfection process. Thesimulated system is an exemplary system according to embodiments of theinvention. The system includes one UV light source within a quartzsleeve positioned in the center of a quartz conduit such that the sleeveis perpendicular to the longitudinal axis of symmetry of the conduitdefining the Z direction. The longitudinal axis of the sleeve definedthe X direction. The calculations were performed for a flow of liquid of50 m³/h. The length of the conduit was taken to be 800 mm, the internaldiameter of the conduit as 75 mm, the external diameter of the sleeveprotecting the UV light source as 44 mm and the pressure drop as ΔP(at50 m³/h)=0.27 [bar]. The liquid used for the computer simulations wasclear water with UVT (ultraviolet transmission) of 98%.

FIG. 12A is a cross section in the Y-Z plane of a portion of the conduitillustrating the light flux distribution between the light source andthe outlet end of the conduit. FIG. 12B is a cross section in the X-Zplane of the same portion of the conduit illustrating the light fluxdistribution between the light source and the outlet end of the conduit.FIG. 12C is a cross section in the Y-Z plane of the entire conduitillustrating the light flux distribution between the inlet end and theoutlet end of the conduit. As can be seen, the light reaches trough theentire length of the tube at a substantial intensity. FIG. 12D shows agraph illustrating the calculated normalized UV dose distribution withinthe quartz conduit. The normalized dose distribution function is closedto being a Gaussian function.

As comparative data, FIGS. 13A and 13B illustrate computer simulationsof light flux distribution within a conventional stainless steelcontainer having 20% reflection during a liquid disinfection process.All the other parameters used in the comparative simulation were similarto the simulations of FIGS. 12A-12C. As can be seen, the intensity oflight is practically zero after 50 mm is the Z direction. FIG. 13C showsa graph illustrating the UV dose distribution within the conventionalstainless steel conduit. As expected, the average dose within thestainless steel conduit having a value of {48 [mJ/cm²]} is much smallerthan the average dose of the quartz conduit with a value of {228[mJ/cm²]}. The dose distribution of the conventional stainless steelconduit is wider than dose distribution of the quartz conduit.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents may occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. An apparatus for liquid disinfection by light, the apparatuscomprising: a substantially light transparent conduit to carry flowingliquid to be disinfected; a substantially light transparent sleevehaving external dimensions smaller than the internal dimensions of theconduit, the sleeve positioned within the conduit substantiallyperpendicular to the axis of symmetry of the conduit; and a light sourcepositioned within the sleeve.